CovVise not only tracks passing tests, but can identify bins which
were only hit by failing tests - extremely interesting points to test further.

CovVise identifies bins that were hit only once or twice
in a test; possibly only due to reset transitions.

CovVise uses hashed objects for all data structures, so that data can
be automatically moved between databases. This allows load sharing between
multiple coverage database servers. For example, the regression system may populate
multiple collection database servers, which in turn feed a master production database.
The production database is then age-purged to an archival database. This allows
scaling to millions of tests per day.